util: Handle UTC wrapping on old Python versions

Old Python versions don't define datetime.UTC, so conditionally import it and
just use the old datetime.utcnow() and datetime.utcfromtimestamp() functions on
those Python versions.

Signed-off-by: Toke Høiland-Jørgensen <[email protected]>

flent/util.py

@@ -37,9 +37,14 @@
 
 from copy import copy
 from calendar import timegm
-from datetime import datetime, timedelta, UTC
+from datetime import datetime, timedelta
 from math import log10, exp, sqrt
 
+try:
+    from datetime import UTC
+except ImportError:
+    UTC = None
+
 from flent.loggers import get_logger
 
 MULTIHOST_SEP = '//'
@@ -68,9 +73,13 @@ def classname(s, suffix=''):
     return uscore_to_camel(s) + suffix
 
 def utcnow():
+    if UTC is None:
+        return datetime.utcnow()
     return datetime.now(UTC).replace(tzinfo=None)
 
 def utcfromtimestamp(ts):
+    if UTC is None:
+        return datetime.utcfromtimestamp(ts)
     return datetime.fromtimestamp(ts, UTC).replace(tzinfo=None)
 
 def format_date(dt, fmt="%Y-%m-%dT%H:%M:%S.%f", utc=False):